Current Federal and State legislation generally requires control of vehicle exhaust emissions. Oxides of Nitrogen (“NOx”) are one of the exhaust gas emissions that must be controlled. Formation of NOx typically occurs at higher combustion temperatures. A system, generally referred to as the exhaust gas recirculation (“EGR”) system, has been developed to reduce combustion temperatures and control NOx emissions. In this type of system, a portion of the exhaust gas is recirculated back to the intake manifold where it is combined with incoming air. When this mixture is compressed and ignited in the cylinder, the result is a lower combustion temperature and a reduction in NOx.
Electric solenoids have been used to provide a number of functions in automotive applications including, but not limited to exhaust gas recirculation valves and the like. These types of systems are generally referred to as solenoid (or solenoid-actuated) exhaust gas recirculation (“SEGR”) systems. These systems typically employ a selectively moveable armature member with a stem or shaft member extending therefrom with a valve member formed at an end thereof that is selectively operable to contact a valve seat so as to allow access to or deny access to, as the case may be, a housing or chamber such that the recirculated exhaust gas may or may not pass therethrough, as the case may be.
Unfortunately, the recirculated exhaust gas contains particulates and vapors (especially acidic compounds) that are potentially harmful to the various components of the solenoid (especially the electrical components) and may cause the solenoid to fail or adversely affect the performance thereof. This problem is exacerbated when any seal around the components of the solenoid valve is poor, especially around the stem member, thus allowing additional recirculated exhaust gas to infiltrate the solenoid.
Therefore, there exists a need for new and improved solenoid valves, especially those with enhanced sealing characteristics about the stem member.